As investigators tried to piece together the motive in a grenade attack on the U.S. Embassy in Montenegro, concerns that the incident could shatter improved stability in the Balkans showed just how fragile the situation remains as the West and Russia battle for influence in the region.

A 43-year-old Serbian war veteran threw an explosive device onto the U.S. Embassy compound in Podgorica overnight Thursday before blowing himself up outside the compound, the Balkan country's police said.

The U.S. State Department said it did not know the motive or whether the assault was meant to be a suicide attack.

Podgorica, Montenegro

But regional experts said it highlights how volatile the situation remains just below the surface in Montenegro, the NATO security alliance's newest member, and the region as a whole.

"Since Jan. 1, we've seen a political assassination in Kosovo, a bombing attack in Montenegro, and Russian-trained paramilitaries assisting the rearming of the Dodik regime in Bosnia. The temperature keeps rising in the Balkans but few in Brussels or Washington seem concerned," said Jasmin Mujanovic, a political analyst and author of Hunger And Fury: The Crisis Of Democracy In The Balkans, based in Durham, North Carolina.

"We will have to see how this develops, as a political point and narrative especially, within the context of the broader confrontation between Russia and the EU and NATO in the region; the target is highly symbolic and charged in that regard, especially given the attacker's apparent military background. And also because of Montenegro's only recent NATO accession, the apparent Russian [attempted] coup to thwart it, and the looming elections which are paving the way for the return of [former Prime Minister] Milo Dukanovic," he added.

Although it's at the center of a historically volatile part of Europe, Montenegro split from Serbia in 2006 without the violence that accompanied similar moves by other republics in the former Yugoslavia, such as Bosnia-Herzegovina, Croatia, and Kosovo.

Podgorica has recognized nearby Kosovo as a sovereign country, something Serbia has refused for a decade to do, yet it also has a sizable Russian population, attracted by its coastline and fair weather.

Still, the Balkan nation of around 600,000 is in the process of tightening cooperation with Washington after becoming the newest NATO ally in June. Its access to the Adriatic makes it a strategic asset for the security alliance, but the move has irked the Kremlin, which is fighting to maintain influence in the region.

People mill around the High Court in Podgorica ahead of the trial of suspects charged with being involved in a coup attempt in 2016.

Montenegrin officials have accused several Serbian and Russian citizens of plotting a coup in 2016 parliamentary elections, claiming they planned to assassinate the prime minister and install a pro-Russian leadership to halt the NATO bid.

'Constant decline of democracy'

The embassy incident also came while Russian Foreign Minister Sergey Lavrov was on a two-day visit to neighboring Serbia, which is juggling its close, warm ties with Moscow with an effort to join the European Union.

"The security situation in the Western Balkans did not worsen in the past years in terms of violence, firearms use, or stability in general. However, the region continues to be a volatile geopolitical arena, with different players involved," said Marika Djolai, a conflict, peace, and development consultant and a London-based member of The Balkans In Europe Policy Advisory Group.

"Issues such as corruption, money laundering, trafficking of drugs, people, and firearms continue to reinforce fragility and threaten stability. There is a trend of constant decline of democracy where the security continues to be an additional burden rather than part of a solution for this problem, showing clear disconnect," she added.

Very short fuse

Even if it may no longer be the powder keg it once was, analysts warned, the Balkan region remains a crisis zone with a very short fuse.

Kosovo, which celebrated a decade of independence earlier this month, is still deeply divided between its dominant majority ethnic-Albanian population and its minority Serbs. The depth of that rift was seen in January with the assassination of a relatively moderate Serbian politician in the northern Kosovar city of Mitrovica and reactions that included Kosovo Prime Minister Ramush Haradinaj's suggestion of "institutions beyond Kosovo."

Mitrovica is a divided city, a front line in the extended standoff between Belgrade, which does not recognize Kosovo, and Pristina. Hardly a month goes by without an incident there, despite the presence of EU and NATO forces.

In Bosnia-Herzegovina, reports of paramilitary formations and news of major arms purchases by the Bosnian Serb police from neighboring Serbia have raised fears that the frozen Yugoslav civil war may be thawing.

Meanwhile Macedonia, which also has a sizable ethnic-Albanian minority, last year almost descended into chaos when scores of demonstrators stormed parliament and attacked several lawmakers after an ethnic Albanian deputy was elected speaker, part of a two-year political crisis that sparked four elections, none of which produced a stable government.

"To prevent political radicalization and ethnic polarization that could ignite armed conflicts, a more vigorous Western Balkan strategy led by Washington is urgently needed," according to Janusz Bugajski, a senior fellow at the Center for European Policy Analysis (CEPA) in Washington.

"Drift and delay in dealing with the Western Balkans can give a false sense of security. After years of relative peace and progress, a new crisis can erupt when ambitious nationalist politicians and foreign governments are intent on provoking armed conflicts to gain power or expand their influence," he added, saying it was too early to determine the impact of the Montenegro attack on policy or the region.